fix: add X connection monitoring for session logout

Added XCB dependency and implemented X server connection monitoring to
detect when the X server disconnects. This ensures the session properly
logs out when the X server connection is lost, preventing orphaned
sessions.

1. Added libxcb1-dev to Build-Depends in debian/control
2. Added XCB pkg-config check and linking in CMakeLists.txt
3. Implemented watchXConnection() method that establishes an XCB
connection and monitors the file descriptor using QSocketNotifier
4. When X connection errors are detected, the session automatically
triggers logout to clean up resources
5. Only activates on X11 displays, not Wayland

This fix addresses cases where X server crashes or disconnects
unexpectedly, leaving the session manager running without a display
server.

fix: 添加X连接监控以实现会话登出

添加XCB依赖并实现X服务器连接监控，以检测X服务器断开连接的情况。这确保当X
服务器连接丢失时会话能正确登出，防止出现孤儿会话。

1. 在debian/control的Build-Depends中添加libxcb1-dev
2. 在CMakeLists.txt中添加XCB pkg-config检查和链接
3. 实现watchXConnection()方法，使用XCB建立连接并通过QSocketNotifier监控
文件描述符
4. 当检测到X连接错误时，会话自动触发登出以清理资源
5. 仅在X11显示环境下激活，Wayland环境下不启用

此修复解决了X服务器崩溃或意外断开连接时，会话管理器在没有显示服务器的情
况下继续运行的问题。

PMS: BUG-353461

Author: mhduiy

debian/control

@@ -16,6 +16,7 @@ Build-Depends:
  libxfixes-dev,
  pkg-config,
  qt6-base-dev,
+ libxcb1-dev,
 Standards-Version: 4.1.3
 Homepage: https://www.deepin.org
 

src/dde-session/CMakeLists.txt

@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: 2023 UnionTech Software Technology Co., Ltd.
+# SPDX-FileCopyrightText: 2023 - 2026 UnionTech Software Technology Co., Ltd.
 #
 # SPDX-License-Identifier: CC0-1.0
 
@@ -14,6 +14,7 @@ pkg_check_modules(GIO2 REQUIRED IMPORTED_TARGET gio-2.0)
 pkg_check_modules(XCURSOR REQUIRED IMPORTED_TARGET xcursor)
 pkg_check_modules(XFIXES REQUIRED IMPORTED_TARGET xfixes)
 pkg_check_modules(X11 REQUIRED IMPORTED_TARGET x11)
+pkg_check_modules(XCB REQUIRED IMPORTED_TARGET xcb)
 
 # dbus adaptor
 qt_add_dbus_adaptor(ADAPTER_SOURCES
@@ -91,6 +92,7 @@ target_link_libraries(dde-session
     PkgConfig::XCURSOR
     PkgConfig::XFIXES
     PkgConfig::X11
+    PkgConfig::XCB
 )
 
 target_include_directories(dde-session PUBLIC

src/dde-session/impl/sessionmanager.cpp

@@ -18,9 +18,11 @@
 #include <QFile>
 #include <QDBusPendingCall>
 #include <QDBusPendingCallWatcher>
+#include <QSocketNotifier>
 
 #include <unistd.h>
 #include <signal.h>
+#include <xcb/xcb.h>
 
 #define MASK_SERVICE(service) \
 {\
@@ -541,9 +543,40 @@ void SessionManager::init()
     startAtSpiService();
     startObexService();
 
+    if (!Utils::IS_WAYLAND_DISPLAY) {
+        watchXConnection();
+    }
+
     qInfo() << "session manager init finished";
 }
 
+void SessionManager::watchXConnection()
+{
+    xcb_connection_t *conn = xcb_connect(nullptr, nullptr);
+    if (xcb_connection_has_error(conn)) {
+        qWarning() << "watchXConnection: failed to connect to X server";
+        xcb_disconnect(conn);
+        return;
+    }
+
+    int fd = xcb_get_file_descriptor(conn);
+    auto *notifier = new QSocketNotifier(fd, QSocketNotifier::Read, this);
+    connect(notifier, &QSocketNotifier::activated, this, [=]() {
+        // 排空所有待处理事件
+        xcb_generic_event_t *ev;
+        while ((ev = xcb_poll_for_event(conn)) != nullptr) {
+            free(ev);
+        }
+        // 若连接已断开则触发登出
+        if (xcb_connection_has_error(conn)) {
+            qWarning() << "X connection closed, logging out";
+            notifier->setEnabled(false);
+            xcb_disconnect(conn);
+            doLogout();
+        }
+    });
+}
+
 void SessionManager::stopSogouIme()
 {
     // TODO 使用kill函数杀死进程，前提是进程存在

src/dde-session/impl/sessionmanager.h

@@ -100,6 +100,7 @@ public Q_SLOTS:
     void setDPMSMode(bool on);
 
     void handleOSSignal();
+    void watchXConnection();
 
     void shutdown(bool force);
     void reboot(bool force);